An MRI apparatus is, when electromagnetic waves are irradiated to an object to be examined placed in a homogeneous static magnetic field, for obtaining a magnetic resonance image (hereinafter referred to as MRI) that represents the physical description of the object by detecting a nuclear magnetic resonance signal (hereinafter referred to as an NMR signal) using NMR phenomenon generated in atomic nuclei of an atom by which the object is constituted and reconstructing an image using the NMR signal.
In MRI, a technique is commonly known for imaging a wide range or whole body of an object while moving a table on which the object is placed in a gantry of an MRI apparatus. In such technique there are the following two methods of moving the table. One is the multi-station imaging method that divides the wide range or the whole body range of the object into a plurality of blocks and performs imaging for each block while moving the table stepwise (for example, refer to Patent Document 1). The other one is the moving table imaging method that images a wide range or a whole body range of the object at one time while continuously moving the table (for example, refer to Patent Document 2).
Patent Document 1: U.S. Pat. No. 6,311,085                Patent Document 2: JP-A-2004-611        
Meanwhile, there is a technique called “shimming” for improving the quality of the images obtained by MRI. Shimming is a method for obtaining a high quality image by correcting the inhomogeneity of static magnetic field generated in an imaging space of in which an object is placed by applying the current to a shim coil whereby enabling to perform imaging in high uniformity condition of static magnetic field (for example, refer to Patent Document 3). Here, there are two kinds of inhomogeneous distribution of the static magnetic field that is a target of shimming: one is apparatus-inherent inhomogeneous distribution of the static magnetic field generated from MRI apparatuses (hereinafter referred to as apparatus-inherent inhomogeneous distribution of the static magnetic field), and the other one is inhomogeneous distribution of the static magnetic field generated inside of the object because every tissue of the object has slightly different magnetic permeability when the object is placed inside of MRI apparatus (hereinafter referred to as object-dependent inhomogeneous distribution of the static magnetic field).                Patent Document 3: JP-A-H11-113880        
As a result of studying the above conventional technique, the present inventors found the problems below. That is, when the above-mentioned table is moved continuously or stepwise while imaging, NMR signals are collected while the table is placed in various positions. In this case, in order to obtain high-quality images by the above-described shimming process, many steps are required since inhomogeneity of static magnetic field must be measured for each table position, whereby consuming a long time for measurement.